The present invention relates to an instrument for urging an orthopedic rod into a recess in an orthopedic device and more particularly, to an instrument for securing a spinal rod to a coupling element.
The spinal column is a highly complex system of bones and connective tissues that provides support for the body and protects the delicate spinal cord and nerves. The spinal column includes a series of vertebral bodies stacked one atop the other, each vertebral body including an inner or central portion of relatively weak cancellous bone and an outer portion of relatively strong cortical bone. Situated between each vertebral body is an intervertebral disc that cushions and dampens compressive forces exerted upon the spinal column. A vertebral canal containing the spinal cord and nerves is located behind the vertebral bodies.
There are many types of spinal column disorders, including scoliosis (abnormal lateral curvature of the spine), kyphosis (abnormal forward curvature of the spine, usually in the thoracic spine), excess lordosis (abnormal backward curvature of the spine, usually in the lumbar spine), spondylolisthesis (forward displacement of one vertebra over another, usually in a lumbar or cervical spine) and other disorders caused by abnormalities, disease or trauma, such as ruptured or slipped discs, degenerative disc disease, fractured vertebra, and the like. Patients that suffer from such conditions usually experience extreme and debilitating pain, as well as diminished nerve function.
Surgical techniques commonly referred to as spinal fixation use surgical implants and/or mechanical immobilization to fuse two or more vertebral bodies of the spinal column. Spinal fixation may also be used to alter the alignment of adjacent vertebral bodies relative to one another so as to change the overall alignment of the spinal column. Such techniques have been used effectively to treat the above-described conditions and, in many cases, to relieve pain.
One spinal fixation technique involves immobilizing the spine using orthopedic stabilizing rods, commonly referred to as spine rods, which are positioned generally parallel to the spine. This may be accomplished by exposing the spine posteriorly and fastening bone screws to the pedicles of vertebral bodies. The pedicle screws are generally placed two per vertebra and serve as anchor points for the spine rods. Coupling elements or implants adapted for receiving a spine rod therethrough are then used to join the spine rods to the pedicle screws. A set screw or fastener then fastens the spine rod into a seat in a coupling element.
Instruments are utilized for inserting a spine rod into position within an orthopedic device such as a coupling element. Surgeons have encountered considerable difficulty when attempting to use these instruments to insert a spine rod into the seat of the coupling element and then inserting a fastener to secure the set up. For example, U.S. Pat. No. 5,910,141 to Morrison provides a rod introduction apparatus capable of laterally aligning a rod with an implant and vertically advancing the rod into position in the implant. The instrument, however, is difficult to use since it requires two hands, one hand to hold the instrument while it clamps the implant and one hand to operate the lateral alignment and vertical alignment means to properly position the rod in the implant.
In addition, U.S. Pat. No. 5,020,519 to Hayes et al. discloses an instrument for seating a spine rod into a hook. The instrument grips the hook with teeth and clamps the hook between the jaws. The thumb wheel must be rotated to shift the pusher thereby urging the spine rod into the hook. Again, it is difficult to utilize this instrument with a single hand.
There remains a need for improved instruments for urging or persuading spinal rods into position in orthopedic devices such as coupling elements or implants. In particular, there remains a need for spinal rod persuaders that may be effectively utilized with one hand. Moreover, there is a need for a simple design that both holds the coupling element stationary while persuading the rod into position. There is a further need for a rod persuader that locks as the rod is advanced into position. It is advantageous for a rod persuader to be easily removed from gripping the coupling element after the rod is properly positioned. It is further advantageous to provide a cannula in the rod persuader in which a set screw or other fastener may be inserted and delivered to the coupling element while the rod persuader is gripping the coupling element and rod.